Positioning sun light to get drop shadow or an object in orthographic view
Things to note, probably including ones you already know:

The location of a Sun lamp makes no difference - it's infinitely far away, and its rays are parallel. Put it somewhere convenient, and adjust only its orientation
The 'angle' setting in the lamp's Data tab &gt; Light panel will harden or soften the shadow
If your World has an HDRI, or is making a contribution through its color, the   the sun's shadow will be somewhat filled by the ambient light.
Shadow Catcher is a Cycles-only feature, and only useful on transparent film.. Corrected! See edit.

EDIT:Thanks to  @blenderbreath, who tells me there's a shadow-catcher for EEVEE, which I've never used ..  Here it is:

I would suggest giving the plane an ordinary diffuse white material during adjustment, to make sure it can be seen at all, before switching its setting to Shadow Catcher